I'm currently running an Elecraft K3/100 - had the matching KPA500 solid state amp, but sold it due to financial issues several months ago. Nice amp, but $2k is a lot of money for a 600-watt amp, in retrospect. Anyway, things have changed and I'm again looking at QRO operation. Not interested in spending a bazillion dollars, so after some research, I think I've set my sights on the Ameritron AL-811HD. I like the idea of having the 572B tubes instead of the 811A's.

I ran the KPA500 on the 117V line in the shack. It worked OK, but I'm pretty sure I I'd be better off getting a 220V line installed in the shack and run the AL-811HD from it, and not off the same circuit as the rest of the room. So, question one - how difficult is it (what is involved) to change the voltage setting on the AL-811HD? The specs say it is "user selectable for 100/110/120/210/220/230 VAC operation".

Question number two - 10/12 meter operation. I thought that I read somewhere on a review that this amp can be made to work on 10 and 12 meters simply be cutting a "green jumper wire". Is this true, or is there another "option" that needs to be purchased and installed?

Question three - there is a $70 inrush current protector offered - worth the money?

My question #1 is why is the 572-B tube listed for the 811-Hd $10.00 less then there regular 572-B tubes ? I want to know that answer first. I think i know the answer but i ask that question. Second It work fine on 120 volts on it's own circuit. #3 well i dont think spend the extra $70.00 on the surge gizmo. Now my opinion if you replace only three of the tubes with 572-B tubes and leave the 4'th hole empty i think you find that the standard AL-811H amp will work quite well that way. In that case i see if they send you one with no tubes and just get 3 from RF Part's And have them knock off the price of the 4 tubes that belonged in it. Or just order it with the 4 811 tubes and then swap oy the tubes and you have spares.

Ameritron can tell you what the 10/12 meter mod is. It's supposed to be a secret.

The 811A tubes are likely more reliable than the 572B tubes in this amp. While the AL-811H uses four unreliable tubes the AL-811 uses only three. So, you can expect 25% less tube failures and an 811A is just $20. While the AL-811H runs higher power on SSB both amps will run 600 watts on CW (even though the manual for the AL-811 says 500 watts).

DX Engineering sells the AL-811 for $709. Note, you will need an RF wattmeter to tune up this amp.

For little more then the cost of a 811HD you can get a real amp, a AL80B. A soft start is a waste of money with this amp as it has a small transformer and uses same one as in 3 tube 811 amp. If you want 572 in a 811 amp get 3 tube version and retube it and you will ge as much output from it as a 4 tube one as the transformer is the limit with 572's in the amp, not 3 tubes. Also you might actually have shorter tube life with 4 572's as the transformer lacks power to load them properly to heat them enough to getter. Also on 10/12 meters just clip the wire.

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--------------------------------------Ham since 1969.... Old School 20 WPM Extra

In general, I agree the with the opinions already offered. You understand that the 572B's won't give you any more power out of an AL811(h) amp. The limiting factor is the power supply.

The 572B's therefore shift the "weak point" in this amplifier from tubes to the power supply. For example, when subjected to serious user errors, the 811 tubes may simply fail, they stop drawing current or blow the AC fuse and that is the end of it. They cost about 20 dollars each and are quickly and easily replaced. The 572B subjected to similar conditions, may not fail and may draw enough current to damage the power supply.

Having said that, I believe the 811 and the 811H represent possibly the best "bang for the buck" in ham radio. Just follow the instructions carefully, tune quickly and WATCH THE GRID CURRENT.

Having said that, I believe the 811 and the 811H represent possibly the best "bang for the buck" in ham radio.

It's astonishing, isn't it? A tube from 1939 was a bit of a sleeper (wasn't even the "RF tube" in the RCA lineup, it was the "AF" tube!) until the late 50's when the 30L1 came out, and today it hits the sweet spot even better in the highly optimized Ameritron amps.

Having said that, I believe the 811 and the 811H represent possibly the best "bang for the buck" in ham radio.

It's astonishing, isn't it? A tube from 1939 was a bit of a sleeper (wasn't even the "RF tube" in the RCA lineup, it was the "AF" tube!) until the late 50's when the 30L1 came out, and today it hits the sweet spot even better in the highly optimized Ameritron amps.

Kinda a counter-diction here. More have trouble with AL811 amps be it tubes or parts than any other amp. Its a shame that no one made a modern SB 200 as even a 35+ year old one that hs been gone through is better amp than a new 811 which are over rated too.

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--------------------------------------Ham since 1969.... Old School 20 WPM Extra

I have a 1993 AL-811 and I am the third owner. The second owner, a friend of mine replaced the tubes as a couple were broken in shipping to him. I recently had to replace the power switch and that is the only problem I have had with it other although I still need to add some capacitance to the 80 meter padding capacitor. I did add the grid protection board when I replaced the switch. I also recently added a 240V line to the shack which is a happy thing!! Switching the amp to 240V is very easy to do. Take a look in the manual which you can download.I would however agree that the AL-80B is the best bang for buck amp out there. If I were going to replace the AL-811, I wouldn't hesitate to buy an AL-80B.

The AL80B looks better after each post. 1 very good forgiving tube the 3-500Z and 800 watts.Looks like a lot of short comings with the modern versions of 572B amps from the past and audio tubes as RF tubes.

The AL80B looks better after each post. 1 very good forgiving tube the 3-500Z and 800 watts.Looks like a lot of short comings with the modern versions of 572B amps from the past and audio tubes as RF tubes.

Fred

Nothing wrong with a 572 in a amp as long as it was designed for it and has a proper power supply. It can use considerably higher plate voltage and current to be fully exploited and non of which a 811 amp can supply.

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--------------------------------------Ham since 1969.... Old School 20 WPM Extra

I have a "regular" 811H amplifier and it works great for me. No problems over the two years I have owned it. Careful on tune up and don't push for the absolute maximum power out.

The 10/12 meter mod is a piece of cake when you find the green wire.

Often audio and seep tubes perform excellently at RF if their internal capacitances to not cause problems. The have to handle longer peak currents at audio, especially bass, than at RF. Ran the same pair of 6LQ6s in a TS511s for 8 years without problems and with a very clean signal too.

Some tubes don't like sloppy operators! Further, what is poison to one tube may not be to another and vice versa. By the way if you keep your duty cycle in mind 800 watts isn't that far out of line for the tubes.

Literally thousands of Collins desktop amps using 4 811 tubes were in service for almost the entire life of the Strategic Air Command, not one of them had a soft start circuit in them. They performed year in and year out, day in and day out, some of the ones I used back in the day were dented, scratched, beat up, repaired Lord knows how many times, and I have even witnessed them being used in lieu of tent pegs. And then placed back into service.

811A "Instant On" tubes -- with unbelievably low starting temps in places like Greenland, then the same amp might be moved to the tropics and used some more.

Literally thousands of Collins desktop amps using 4 811 tubes were in service for almost the entire life of the Strategic Air Command, not one of them had a soft start circuit in them. They performed year in and year out, day in and day out, some of the ones I used back in the day were dented, scratched, beat up, repaired Lord knows how many times, and I have even witnessed them being used in lieu of tent pegs. And then placed back into service.

811A "Instant On" tubes -- with unbelievably low starting temps in places like Greenland, then the same amp might be moved to the tropics and used some more.

Literally thousands of Collins desktop amps using 4 811 tubes were in service for almost the entire life of the Strategic Air Command, not one of them had a soft start circuit in them. They performed year in and year out, day in and day out, some of the ones I used back in the day were dented, scratched, beat up, repaired Lord knows how many times, and I have even witnessed them being used in lieu of tent pegs. And then placed back into service.

811A "Instant On" tubes -- with unbelievably low starting temps in places like Greenland, then the same amp might be moved to the tropics and used some more.

Just sayin'...

73

Ah... but were those 811 tubes the current "Made in China" version?

And the cost those amps new in todays dollars would be around 5 figures too. Not to mention very high quality too.

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--------------------------------------Ham since 1969.... Old School 20 WPM Extra

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